Alto Professional AX2304 | Professional High-Precision Stereo 2-Way / 3-Way/Mono 4-Way Crossover Absolutely flat summed amplitude response with zero phase difference 24 dB-per-octave Linkwitz-Riley filters Individual output level controls for all bands Limiters on each output for optimal loudspeaker protection Switchable 25 Hz subsonic filter on each input for low-frequency driver protection Absolutely flat summed amplitude response with zero phase difference^ 24 dB-per-octave Linkwitz-Riley filters^ Individual output level controls for all bands^ Limiters on each output for optimal loudspeaker protection^ Switchable 25 Hz subsonic filter on each input for low-frequency driver protection